It seems like it was inevitable.  Disney had a HUGE hit on its hands with the animated movie "Frozen."  According to Screen Crush, it's already grossed $400 million in the U.S. and more than $1.2 billion worldwide. and now after a shareholder's meeting, they've made it official that they are coming out with a sequel to Frozen.

They've already made the announcement that Frozen would be seeing the stage on Broadway but up until now, Frozen 2 has only been a rumor.  Now it's official.  Disney will be releasing a sequel to the box office smash.

We enjoyed making “Frozen Fever” so much and being back in that world with those characters. Jennifer Lee and Chris Buck have come up with a great idea for a sequel and you will be hearing a lot more about it and we’re taking you back to Arendelle. We are so excited about that.” - Disney Chief Creative Officer John Lasseter
All of the original cast is expected too.  At least one of them seemed excited about it as she took to twitter:

There is no word as to when we can expect it in theaters but at least we know that now it's not just a rumor.